cmp.c

Go to the documentation of this file.

/* cmp - compare two files              Author: Kees J. Bot.  */

#include <sys/types.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>

_PROTOTYPE(void fatal, (char *label));
_PROTOTYPE(int cmp, (int fd1, int fd2));
_PROTOTYPE(void Usage, (void));
_PROTOTYPE(int main, (int argc, char **argv));

#define BLOCK   4096

static int loud = 0, silent = 0;
static char *name1, *name2;

int main(argc, argv)
int argc;
char **argv;
{
  int fd1, fd2;

  /* Process the '-l' or '-s' option. */
  while (argc > 1 && argv[1][0] == '-' && argv[1][1] != 0) {
        if (argv[1][2] != 0) Usage();

        switch (argv[1][1]) {
        case '-':
                /* '--': no-op option. */
                break;
        case 'l':
                loud = 1;
                break;
        case 's':
                silent = 1;
                break;
        default:
                Usage();
        }
        argc--;
        argv++;
  }
  if (argc != 3) Usage();

  /* Open the first file, '-' means standard input. */
  if (argv[1][0] == '-' && argv[1][1] == 0) {
        name1 = "stdin";
        fd1 = 0;
  } else {
        name1 = argv[1];
        if ((fd1 = open(name1, 0)) < 0) fatal(name1);
  }

  /* Second file likewise. */
  if (argv[2][0] == '-' && argv[2][1] == 0) {
        name2 = "stdin";
        fd2 = 0;
  } else {
        name2 = argv[2];
        if ((fd2 = open(name2, 0)) < 0) fatal(name2);
  }

  exit(cmp(fd1, fd2));
}

int cmp(fd1, fd2)
int fd1, fd2;
{
  static char buf1[BLOCK], buf2[BLOCK];
  int n1 = 0, n2 = 0, i1 = 0, i2 = 0, c1, c2;
  off_t pos = 0, line = 1;
  int eof = 0, differ = 0;

  for (;;) {
        if (i1 == n1) {
                pos += n1;

                if ((n1 = read(fd1, buf1, sizeof(buf1))) <= 0) {
                        if (n1 < 0) fatal(name1);
                        eof |= 1;
                }
                i1 = 0;
        }
        if (i2 == n2) {
                if ((n2 = read(fd2, buf2, sizeof(buf2))) <= 0) {
                        if (n2 < 0) fatal(name2);
                        eof |= 2;
                }
                i2 = 0;
        }
        if (eof != 0) break;

        c1 = buf1[i1++];
        c2 = buf2[i2++];

        if (c1 != c2) {
                if (!loud) {
                        if (!silent) {
                                printf("%s %s differ: char %ld, line %ld\n",
                                       name1, name2, pos + i1, line);
                        }
                        return(1);
                }
                printf("%10ld %3o %3o\n", pos + i1, c1 & 0xFF, c2 & 0xFF);
                differ = 1;
        }
        if (c1 == '\n') line++;
  }
  if (eof == (1 | 2)) return(differ);
  if (!silent) fprintf(stderr, "cmp: EOF on %s\n", eof == 1 ? name1 : name2);
  return(1);
}

void fatal(label)
char *label;
{
  if (!silent) fprintf(stderr, "cmp: %s: %s\n", label, strerror(errno));
  exit(2);
}

void Usage()
{
  fprintf(stderr, "Usage: cmp [-l | -s] file1 file2\n");
  exit(2);
}

---